Determination of thickness and impurity profiles in thin membranes utilizing spectorscopic data obtained from ellipsometric investigation of both front and back surfaces

Abstract

Disclosed is spectroscopic ellipsometer system mediated methodology for quantifying thickness and impurity profile defining parameters in mathematical models of impurity profile containing thin membranes having two substantially parallel surfaces which are separated by a thickness, wherein the spectroscopic ellipsometer system operates in near-IR and IR wavelength ranges.

We claim:  
     
       1. A method of quantifying thickness and impurity profile defining parameters in impurity profile containing membranes, comprising the steps of providing an ellipsometer system, and sequentially or simultaneosly obtaining ellipsometric data sets from both first and second sides of an impurity profile containing membrane, and providing a mathematical model of said impurity profile defining parameters comprising membrane thickness and impurity profile defining parameters, then performing a mathematical regression of said mathematical model onto data obtained from said impurity profile containing membrane by a selection from the group consisting of: 
       utilizing the data sets obtained from front and back of the thin membrane simultaneously;  
       utilizing the data sets obtained from front and back of the thin membrane independently; and  
       utilizing the data sets obtained from front and back of the thin membrane both independently and simultaneously.  
       to evaluate said membrane thickness and impurity profile defining parameters. 
     
     
       2. A method of quantifying thickness and impurity profile defining parameters in impurity profile containing membranes comprised of two substantially parallel surfaces that are separated by a thickness, said method comprising the steps of: 
       a. providing an impurity profile containing membrane comprised of two substantially parallel surfaces that are separated by a thickness, and providing a spectroscopic ellipsometer system capable of producing spectroscopic data sets at at least one angle of incidence of a beam of electromagnetic radiation to a surface of said impurity profile containing membrane when it is mounted in said spectroscopic ellipsometer system;  
       practicing steps b. and c. in either order: 
       b. determining a range of wavelengths over which the impurity profile containing membrane is essentially transparent and the effect of the presence of said impurity profile has essentially negligible effect;  
       c. determining a range of wavelengths over which the impurity profile containing membrane is essentially transparent, but over which the effect of the presence of said impurity profile has a non-negligible effect;  
       practicing steps d., e. and f. in any order, including the possibility of performing two or more steps simultaneously: 
       d. utilizing substantially wavelengths in the range determined in step b., by an approach selected from the group consisting of:  
       reflection ellipsometry; and  
       transmission ellipsometry;  
       obtaining a spectroscopic data set; 
       e. utilizing wavelengths in the range determined in step c., by reflection ellipsometry as applied to one surface of said impurity profile containing membrane, obtaining a spectroscopic data set;  
       f. utilizing wavelengths in the range determined in step c., by reflection ellipsometry as applied to a surface of said impurity profile containing membrane offset from that utilized in step e. by said thickness, obtaining a spectroscopic data set;  
       in conjunction with the foregoing steps, practicing steps g. and h. in either order: 
       g. providing a mathematical model for said impurity profile containing membrane including a parameter that quantifies thickness;  
       h. providing a mathematical model for said impurity profile containing membrane including parameters that quantify impurity profile defining parameters;  
       i. using the spectroscopic data set obtained in step d., performing a mathematical regression of the mathematical model provided in step g. thereonto to evaluate the parameter that quantifies thickness;  
       j. using the thickness arrived at in step i. and the spectroscopic data sets obtained in at least one of the steps e. and f., simultaneously performing a mathematical regression of the mathematical model provided in step h. thereonto to evaluate the parameters that quantify the impurity profile.  
     
     
       3. A method of quantifying thickness and impurity profile defining parameters in impurity profile containing membranes comprised of two substantially parallel surfaces that are separated by a thickness, said method comprising the steps of: 
       a. providing an impurity profile containing membrane comprised of two substantially parallel surfaces that are separated by a thickness, and providing a spectroscopic ellipsometer system capable of producing spectroscopic data sets at at least one angle of incidence of a beam of electromagnetic radiation to a surface of said impurity profile containing membrane when it is mounted in said spectroscopic ellipsometer system;  
       practicing steps b. and c. in either order: 
       b. determining a range of wavelengths over which the impurity profile containing membrane is essentially transparent and the effect of the presence of said impurity profile has essentially negligible effect;  
       c. determining a range of wavelengths over which the impurity profile containing membrane is essentially transparent, but over which the effect of the presence of said impurity profile has a non-negligible effect;  
       practicing steps d., e. and f. in any order, including the possibility of performing two or more steps simultaneously: 
       d. utilizing substantially wavelengths in the range determined in step b., by an approach selected from the group consisting of:  
       reflection ellipsometry; and  
       transmission ellipsometry;  
       obtaining a spectroscopic data set; 
       e. utilizing substantially wavelengths in the range determined in step c., by reflection ellipsometry as applied to one surface of said impurity profile containing thin membrane, obtaining a spectroscopic data set;  
       f. utilizing substantially wavelengths in the range determined in step c., by reflection ellipsometry as applied to a surface of said impurity profile containing membrane offset from that utilized in step e. by said thickness, obtaining a spectroscopic data set;  
       g. in conjunction with the foregoing steps providing a mathematical model for said impurity profile containing membrane including parameters that quantify thickness and impurity profile defining parameters;  
       h. using all obtained spectroscopic data sets, simultaneously performing mathematical regression of the mathematical model thereonto to evaluate the parameters that quantify thickness and the impurity profile defining parameters.